Compressed-gas circuit breaker

ABSTRACT

A compressed-gas circuit breaker such as a high-voltage power breaker and the like is disclosed. The circuit breaker has two stationary contact pieces mutually adjacent and defining a gap therebetween. Each of the contact pieces is of hollow configuration for accommodating the passage of the gas. A primary switching member is movable between open and closed positions for electrically bridging the contact pieces in the closed position and an auxiliary switching member is mounted so as to be slideable in the contact pieces for electrically opening and closing the gap. A drive moves the primary switching member between the open and closed positions. A coupling couples the auxiliary switching member to the drive to cause the auxiliary switching member to open the gap after the elapse of a time interval commencing at the separation of the primary switching member from at least one of the contact pieces during the movement of the primary switching member to the open position whereby the primary switching member switches without an arc at the separation and whereby the auxiliary switching member draws an arc when the gap is opened. A gas-blast arrangement actuated by the drive blasts a stream of gas through the arc when the primary switching member is moved to the open position.

United States Patent [191 Marin Apr. 2, 1974 COMPRESSED-GAS CIRCUIT BREAKER voltage power breaker and the like is disclosed. The [75] Inventor: Rein" Marin Berlin Germany circuit breaker has two stationary contact pieces mutually adjacent and defining a gap therebetween. Each [73] Assigneei Siem ns Akfi llg hafl, u of the contact pieces is of hollow configuration for ac- Ge m ny commodating the passage of the gas. A primary [22] Filed: Man 1, 1973 switching member is movable between open and 211 Appl. No.: 337,174

Primary Examiner kobert S. Macon Attorney, Agent, or FirmKeny0n & Kenyon Reilly Carr & Chapin [57] ABSTRACT A compressed-gas circuit breaker such as a highclosed positions for electrically bridging the contact pieces in the closed position and an auxiliary switching member is mounted so as to be slideable in the contact pieces for electrically opening and closing the gap. A drive moves the primary switching member between the open and closed positions. A coupling couples the auxiliary switching member to the drive to cause the auxiliary switching member to open the gap after the elapse of a time interval commencing at the separation of the primary switching member from at least one of the contact pieces during the movement of the primary switching member to the open position whereby the primary switching member switches without an are at the separation and whereby the auxiliary switching member draws an are when the gap is opened. A gas-blast arrangement actuated by the drive blasts a stream of gas through the are when the primary switching member is moved to the open position.

14 Claims, 1 Drawing Figure LibUlf/GB LAIENTEBAPR 2 1974 l COMPRESSED-GAS CIRCUIT BREAKER BACKGROUND OF THE INVENTION A power circuit breaker wherein the arc is quenched by means of a flow of compressed gas is known from Deutsche Auslegungsschrift 1,156,143. This circuit breaker includes a hollow contact pin through which the quenching medium flows and a tubular switching element movable with respect to the pin. During the disconnect operation, the switching element is pushed by spring action past the end of the contact pin facing an opposite contact element, and which, during switch closure, is pushed back from the opposite contact element against the spring action. In conjunction with the contact pin, a pumping device is activated which urges the pressurized gas into the area of the arc.

The contact pin in this known arrangement is still closed to the flow of quenching agent at. the beginning of the interrupting cycle because the switching element does not follow the'movement of the contact pin at once; rather, the switching element extends beyond the end of the contact facing the adjacent contact and is pushed against the adjacent contact. The pumping device is activated simultaneously with the contact pin and subjects the quenching medium to pressure until the tubular switching element is carried along after a predetermined movement of the contact pin. At this instant, that is after the lost motion is overcome, there results a particularly intense flow of quenching medium due to the prior compression of this medium. Furthermore, the final contact break takes place at a comparatively great velocity, since the contact pin has previously been accelerated. However, in the blast-piston circuit breaker there are limits to the attainable contact velocity: first, because of the large masses which have to be accelerated, and second, because of the necessity of accomplishing the pressurization and release of the quenching gas within a permissible contact displacement and within the specified arc duration.

To reduce the loading of the power system to a minimum, it is frequently desirable to quench the arc with certainty by the end of the second wave period after the disturbance actuating the breaker has occurred. In a blast-piston breaker, the total switching time, or more specifically the time from the command for opening the switching elements to the first quenching of the arc,

comprises: the response time which is designated as the,

relay-switching delay, the time for pressurizing the gas, and the minimum arc quenching time.

SUMMARY OF THE lNVENTlON Accordingly, it is an object of the invention to reduce the minimum quenchingtime of a blast-piston type circuit breaker operating according to the blast-piston principle. Subsidiary to this object, it is an object ofthe invention to provide a compressed-gas circuit breaker wherein the minimum quenching time is reduced without an increase in the energy of. the drive.

The invention relates to a gas-pressure circuit breaker, particularly a, high-voltage, high-power breaker with a blasting facility for the quenching gas including a cylinder-and a piston. The breaker has hollow tubular contacts through which the quenching gas can flow andwhich are connected in an electricallyconducting manner when the breaker is closed. Also provided is an additional auxiliary switching member 2 which openswith a delay the gap between the contacts while the breaker is being opened; this auxiliary switch ing member then draws the arc. The invention provides a compressed-gas breaker which reduces the minimum arc quenching time. v

The compressed-gas circuit breaker of the invention includes as a feature two stationary contact pieces mutually adjacent and defining a gap therebetween. Each of the contact pieces is of hollow configuration for accommodating the passage of the gas. A primary switching member is movable between open and closed positions for electrically bridging the contact pieces in the closed position and an auxiliary switching member is mounted so as to be slideable in the contact pieces for electrically opening and closing the gap. A drive moves the primary switching member between the open and closed positions. A coupling couples the auxiliary switching member to the drive to cause the auxiliary switching member to open the gap after the elapse of a time interval commencing at the separation of the primary switching member from at least one of the contact pieces during the movement of the primary switching member to the open position whereby the primary switching member switches without an are at the separation and whereby the auxiliary switching member draws an arc'when the gap is opened. A gas blast arrangement actuated by the drive blasts a stream of gas through the are when the primary switching member is moved to the open position. Utilizing the invention makes it possible to dispense with sliding contact elements which surround the moving switching elements in an electrically conductive manner under spring load. The primary switching member which bridges the stationary contact pieces switches without an arc; as the main current carrier, it is constructed with sufficient cross-section to carry rated current continuously and short-circuit current for a short interval. The auxiliary switching member draws the arc and is guided inside the stationary contacts with a sliding motion. During the circuit-opening motion of this switching member and during the time that the arc is to be drawn, the requirements of the contact are comparatively so small that a loose fit without sliding contact pieces is sufficient.

The auxiliary switching member is guided to as to be slideable inside the stationary contact pieces and draws the arc in'a favorable manner to the vicinity of the axis of the two hollow stationary contact pieces. And, the auxiliary switching member moves via coupling means in the form of a free-running thrust coupling with the drive, after overcoming the lost motion which is provided, with a velocity that can be almost twice as great as the drive velocity for the primary switching member and the blasting arrangement.

Preferably, the mass of the moving auxiliary switching member is at most one-tenth of the moving mass of the drive. In practice, the velocity imparted to the auxiliary switching member by the thrust coupling will be lower than theoretically possible because of inevitable friction losses. Nevertheless it is possible to reduce the minimun quenching time significantly by raising the opening velocity of the auxiliary switching member.

According to a further feature of the invention, the

coupling means comprises two parts having a common axis and mounted so as to be movable along this axis. One of these parts is rigidly coupled to the drive and the other one of the parts is rigidly coupled to the auxiliary switching member. Also included are striker means for mutually engaging the parts during the movement of the primary switching member at the conclusion of the time interval to move the other part along the axis with the one part thereby opening the gap. According to a subsidiary feature, these parts can be respective tubular members defining an interface therebetween, the striker means being stops mounted at this interface so as to define limits within which the one part can move along the axis relative to said other part. I

Thus, in a preferred embodiment of the compressedgas circuit breaker according to the invention the freerunning thrust coupling comprises two tubular, coaxially oriented parts, axially movable between stops, one part being rigidly coupled to the auxiliary switching member, and the other, tothe drive. Here the cooperating thrust surfaces of the thrust coupling are themselves provided-by the stops. Subsidiary to this embodiment, it is possible to provide resilient intermediate members having only minimal friction, particularly internal friction. Thus the thrust surfaces cannot be permanently deformed even after frequent applications of the thrust.

In a further embodiment of the invention, the primary switchingmember which switches at zero current forms,'at least partially, the blast cylinder, which during the opening motion is pulled over a blast piston fixed in a position with respect to the cylinder; The primary switching member is advantageously separated electrically from both stationary contact pieces outside the closed position. Thus it is possible to dispense with sliding contact pieces. The auxiliary switching member preferably consists of an arc-resistant material and can be electrically separated from both stationary contact pieces outside the closed position. Preferably, in the open position of the breaker, the auxiliary switching member in the compressed-gas circuit breaker of the invention assumes a position inside one of the fixed contact pieces which does not inhibit-the removal of switching gases. The auxiliary switching member is preferably of tubular construction. I

Theauxiliary switching member advantageously is electrically insulated from the drive. This insulation shouldbe able to withstand the arc separation potential so that, during the opening of the gap, the current flows from the nozzle -of one nozzle-like contact piece through the arc-resistant auxiliary switching member to thenozzle of the other nozzle-like Contact piece.

Although the invention is illustrated and described herein as a compressed-gas circuit breaker, it is nevertheless not intended to be limited to the details shown, since various modifications may be made therein within the scope and the range of the claims. The invention, however, together with additional objects and advantages will be best understood from the following description and in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWING The drawing is a schematic diagram, in longitudinal section, of a compressed-gas circuit breaker according to the invention. The left-half of the diagram shows the primary switching member in the open position and the right half, the'closed position. The circuit breaker can use sulfur hexafluoride as the quenching and insulating medium. To afford a clear view, only the parts required for understanding the invention are shown and'breaker parts such as'those at ground potential, particularly the drive and'the supporting insulators, are not shown.

DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION The electric circuit breaker is constructed as a compressed-gas breaker and includes a switching chamber 1 made of porcelain for example. Within the chamber 1, two stationary switching contact pieces 2 and 3 are arranged which carry nozzles 4 and 5 constructed of arc-resistant material at their respective mutually adjacent ends. The two contact pieces 2 and.3 are made hollow for directing the switching gases away. In the closed position of the breaker shown to the right of the center line, the switching contact pieces are connected by an electrically-conducting bridging switch member 6 of tubular construction. The member 6 can be considered as being the primary switching member. The

upper and lower edges of the switching member 6 carry I contact elements 7 which are pressedby a contactmaking spring force against parts 20 and 3a of the stationary contact pieces 2 and 3 respectively.

The end of the switching member 6 facing the stationary contact piece 2 carries a nozzle 8 having a central bore 9. which surrounds the contact piece 2. The switching member 6 is coupled by means of pins 10 to the drive member 11 which in turn is driven by a connecting-rod 12 in the direction of the arrow 13. The drive member 11 is connected to the auxiliary switching member 14 by coupling means in the form ofa freerunning thrust coupling 15, 16in such a way that, during the disconnect movement, the auxiliary switching member 14 is opened at a time delayed with respect to the opening of switching member 6. The auxiliary switching memberl4 is mounted in a manner'permitting sliding motion inside the stationary switching contactp'ieces 2, 3 and draws the are into the vicinity of the centerof the contact pieces 2 and-3 in the region of the nozzles 4,and 5. Therefore, the auxiliary switching member 14 as well as the nozzles 4 and 5 are preferably constructed of an arc-resistant, electricallyconducting material. Y

The thrust coupling 15, 16 is located inside the contact piece 3 and includes two tubular, coaxiallydisposed parts 15a and 16a. The tubular part 15a carries the auxiliary switching member 14 and includes on its end facing away from the member 14, a stop in the form of a protruding edge portion 17 having striking and thrust surfaces. The edge portion 17 of the tubular part 15a can move freely between the two stops configured as protruding outer edge portions 18 and 19 on the outer periphery of tubular part 16a which is rigidly coupled to the drive member 11 so that there is a limited axial movement between tubular parts 15a and 16a. The coacting striking and thrust surfaces of the edge portions l7, l8 and 17, 19 are stops which limit the axial movement. Resilient intermediate members 20 and 21 are provided with the member 21 exhibiting a low inner friction.

The inner contour of the nozzle 8 is fitted to a part of the stationary contact piece 3; this part constitutes the fixed piston 22 of the blast arrangement. The switching member 6 constitutes the blast cylinder and, during the disconnect movement, is pulled over this stationary blast piston 22 so that the operation described below is obtained.

During the first part of the disconnect movement, the stationary contact pieces 2 and 3 are electrically connected by the auxiliary switching member 14. For this reason, the switching member 6 switches without an arc. As the disconnect movement proceeds, with pressurization in the compression space 23 of the sulphurhexafluoride gas used as the quenching medium, the pressure is increased until the stop 19 slams against the protruding edge portion 17' causing the auxiliary switching member 14 to be pushed in the direction of the disconnect movement. The arc which is thereby drawn to the center of the switching contacts is subjected to the intense blast of the pre-compressed quenching gas. The separating velocity of the auxiliary switching member 14 is approximately twice the movement velocity of the primary switching member 6 because, due to the small amount of friction of the auxiliary switching member 14 in the region of nozzles 4 and 5, the velocity of the auxiliary switching member 14 obeys the principle of the conservation of momentum. This means that a high separating velocity develops which reduces the effective duration of the arc. This results in a shortened arc-radiation time. Furthermore, because of the reduced arc duration, fewer decomposition products are generated.

The drawing shows that the primary switching member is electrically separated from both stationarycontacts in the open position of the breaker. Similarly, the auxiliary switching member 14 is electrically separated from both stationary contact pieces 2 and 3 outside the closed position of the breaker. For this purpose, the tubular part 15a can contain an electrically insulating guide or can be itself made of insulating material. The auxiliary switching member 14 can be configured so as to tubular and, in the open position of the switch, assumes inside the contact 3 a position that does not inhibit the exhaust of the switching gases.

The switching gases are removed through the nozzles 4 and 5 of thestationary contact pieces 2 and 3. The stationary contact piece 3 can be provided with passage openings 24'for the passage of switching gases. Similarly it is possible to provide the tubular part 15a with openings 25 for the passage of switching gases.

The compressed-gas circuit breaker according to the invention includes an'arc-drawing auxiliary switching member which opens the gap between the switching contact pieces on a delayed basis during the disconnect movement of the breaker and has a short switching time because the minimum quenching time is reduced by a high separating velocity as compared to the breakers'of known construction.

What is claimed is:

l. A compressed-gas circuit breaker such as a highvoltage power breaker and the like comprising two stationary contact pieces mutually adjacent and defining a gap therebetween, each of said contact pieces having a hollow configuration for accommodating the passage of the gas; a primary switching member movable between open and closed positions for electrically bridging said contact pieces in the closed position; an auxiliary switching member mounted so as to be slideable in said contact pieces for electrically opening and closing said gap; a drive for moving said primary switching member between said open and closed positions; coupling means for coupling said auxiliary switching member to said drive to cause said auxiliary switching member to open said gap after the elapse of a time interval commencing at the separation of said primary switching member from at least one of said contact pieces during the movement of said primary switching member to said open position whereby said primary switching member switches without an arc at said separation and whereby said auxiliary switching member draws an are when said gap is opened; and gas-blast means actuated by said drive for blasting a stream of gas through the arc when said primary switching member is moved to said open position.

2. The compressed-gas circuit breaker of claim 1, said coupling means comprising two parts having a common axis and mounted so as to be movable along said axis, one of said parts being rigidly coupled to said drive and the other one of said parts being rigidly cou pled to said auxiliary switching member, and striker means for mutually engaging said parts during the movement of said primary switching member at the conclusion of said time interval to move said other part along said axis with said one part thereby opening said gap.

3. The compressed-gas circuit breaker of claim 2, said parts being respective tubular members defining an interface therebetween, said striker means being stops mounted at said interface so as to define limits within which said one part can move along said axis relative to said other part.

4. The compressed-gas circuit breaker of claim 3, said stops having respective striking surfaces coacting to move said auxiliary switching member along said axis.

5. The compressed-gas circuit breaker of claim 4 comprising resilient intermediate members disposed between said coacting striking surfaces.

6. The compressed-gas circuit breaker of claim 1 wherein the mass of said auxiliary switching member corresponds to at most one-tenth of the mass of said drive.

7. The compressed-gas circuit breaker of claim 1, said gas-blast means comprising a cylinder for holding the gas therein, and a piston mounted in said cylinder, said cylinder and said piston being mounted with respect to said gap so as to cause a relative movement between said piston and said cylinder when said primary switching member moves to said open position to impart sufficient energy to the gas for blasting the same through the arc.

8. The compressed-gas circuit breaker of claim 7, said cylinder being constituted at least in part by said primary switching member.

9. The compressed-gas circuit breaker of claim 1 wherein said primary switching member is separated electrically from both of said stationary contact pieces when said primary switching member is outside of said closed position.

10. The compressed-gas circuit breaker of claim 1, said auxiliary switching member being made of areresistant material.

11. The compressed-gas circuit breaker of claim 1, said auxiliary switching member having a tubular configuration.

12. The compressed-gas circuit breaker of claim 1 wherein said auxiliary switching member is separated electrically from said stationary contact pieces in said open position of said primary switching member.

13. The compressed-gas circuit breaker of claim 1 wherein said drive and said coupling means coact to move said auxiliary switching member to a position blasted through the are by said gas-blast means. whereat the same is withdrawn from said contact pieces 14. The compressed-gas circuit breaker of claim 1, when said primary switching member is in said open said auxiliary switching member being electrically insu position whereby the respective hollows of said,contact lated with respect to said drive. pieces afford an unobstructed passage to the gas 

1. A compressed-gas circuit breaker such as a high-voltage power breaker and the like comprising two stationary contact pieces mutually adjacent and defining a gap therebetween, each of said contact pieces having a hollow configuration for accommodating the passage of the gas; a primary switching member movable between open and closed positions for electrically bridging said contact pieces in the closed position; an auxiliary switching member mounted so as to be slideable in said contact pieces for electrically opening and closing said gap; a drive for moving said primary switching member between said open and closed positions; coupling means for coupling said auxiliary switching member to said drive to cause said auxiliary switching member to open said gap after the elapse of a time interval commencing at the separation of said primary switching member from at least one of said contact pieces during the movement of said primary switching member to said open position whereby said primary switching member switches without an arc at said separation and whereby said auxiliary switching member draws an arc when said gap is opened; and gas-blast means actuated by said drive for blasting a stream of gas through the arc when said primary switching member is moved to said open position.
 2. The compressed-gas circuit breaker of claim 1, said coupling means comprising two parts having a common axis and mounted so as to be movable along said axis, one of said parts being rigidly coupled to said drive and the other one of said parts being rigidly coupled to said auxiliary switching member, and striker means for mutually engaging said parts during the movement of said primary switching member at the conclusion of said time interval to move said other part along said axis with said one part thereby opening said gap.
 3. The compressed-gas circuit breaker of claim 2, said parts being respective tubulaR members defining an interface therebetween, said striker means being stops mounted at said interface so as to define limits within which said one part can move along said axis relative to said other part.
 4. The compressed-gas circuit breaker of claim 3, said stops having respective striking surfaces coacting to move said auxiliary switching member along said axis.
 5. The compressed-gas circuit breaker of claim 4 comprising resilient intermediate members disposed between said coacting striking surfaces.
 6. The compressed-gas circuit breaker of claim 1 wherein the mass of said auxiliary switching member corresponds to at most one-tenth of the mass of said drive.
 7. The compressed-gas circuit breaker of claim 1, said gas-blast means comprising a cylinder for holding the gas therein, and a piston mounted in said cylinder, said cylinder and said piston being mounted with respect to said gap so as to cause a relative movement between said piston and said cylinder when said primary switching member moves to said open position to impart sufficient energy to the gas for blasting the same through the arc.
 8. The compressed-gas circuit breaker of claim 7, said cylinder being constituted at least in part by said primary switching member.
 9. The compressed-gas circuit breaker of claim 1 wherein said primary switching member is separated electrically from both of said stationary contact pieces when said primary switching member is outside of said closed position.
 10. The compressed-gas circuit breaker of claim 1, said auxiliary switching member being made of arc-resistant material.
 11. The compressed-gas circuit breaker of claim 1, said auxiliary switching member having a tubular configuration.
 12. The compressed-gas circuit breaker of claim 1 wherein said auxiliary switching member is separated electrically from said stationary contact pieces in said open position of said primary switching member.
 13. The compressed-gas circuit breaker of claim 1 wherein said drive and said coupling means coact to move said auxiliary switching member to a position whereat the same is withdrawn from said contact pieces when said primary switching member is in said open position whereby the respective hollows of said contact pieces afford an unobstructed passage to the gas blasted through the arc by said gas-blast means.
 14. The compressed-gas circuit breaker of claim 1, said auxiliary switching member being electrically insulated with respect to said drive. 